PDS_VERSION_ID = PDS3 LABEL_REVISION_NOTE = " 2018-08-10, Maud Barthelemy first draft. 2019-07-18, David Heather. Updated following comments from first review. 2020-06-01, David Heather. Updated following comments from close-out review." RECORD_TYPE = STREAM OBJECT = INSTRUMENT INSTRUMENT_HOST_ID = "RO" INSTRUMENT_ID = "SREM" OBJECT = INSTRUMENT_INFORMATION INSTRUMENT_NAME = "STANDARD RADIATION ENVIRONMENT MONITOR" INSTRUMENT_TYPE = "PARTICLE DETECTOR" INSTRUMENT_DESC = " For detailed information on the SREM instrument, see also the following website: http://srem.web.psi.ch Instrument Overview ======== Specifications -------------- NAME: SREM (Standard Radiation Environment Monitor) DESCRIPTION: Particle detector, developed for space applications measuring high energy electrons and protons PRINCIPAL INVESTIGATORS: Hugh Evans, Petteri Nieminen ENERGY RANGE: electrons 0.5 MeV (minimum) protons 10 MeV (minimum) ANGULAR RESOLUTION: 20 degrees ENERGY LEVELS: 15 bins Dimension 96 mm x 122 mm x 217 mm Weight 2.5 kg Power consumption 2.5 W Description ----------- SREM, the successor to the REM instrument, is a particle detector developed for space applications, designed to measure electrons with energies E > 0.5 MeV and protons with energies E > 10 MeV, with an angular resolution of 20 degrees. The SREM measurements provide the host spacecraft with environmental radiation information. SREMs have flown on several satellites: Strv-1c, Proba-1, Integral, Rosetta, GIOVE-B, Herschel, and Planck, and additional missions are to follow. SREM was developed and manufactured by oerlikon space in cooperation with Paul Scherrer Institute under a development contract of the European Space Agency. Top level design ----------------- The Standard Radiation Environment Monitor comprises one box of 2.5 kg with dimensions of 96 mm x 122 mm x 217 mm. The box houses the following functional blocks: - Power supply with DC/DC converter with output voltages for the digital and the analog circuits, as well as for the detectors. - Three particle detectors with associated temperature sensors integrated in the detector housing. - Analog front end with low noise signal amplifiers and signal conditioning electronics. - Comparators with fifteen detection ranges. - Interface for remote total dose and temperature measurement sensors. - Signal processing electronics with host spacecraft interface for: 1. Data processing and storage of scientific data 2. Acquisition of housekeeping data and system health monitoring 3. Telemetry and telecommand interface with host spacecraft. The three solid state detectors (silicon diodes) measure the energy deposited by charged particles. These diodes (D1, D2, D3) are arranged as follows: D3 is a single diode for detection of both protons and electrons. D1 and D2 are two single diodes combined together in a telescope configuration. They can therefore be used separately or in a coincidence mode, where a particle is required to deposit energy in both of them simultaneously. D1 and D2 are separated by a double layer of aluminium and tantalum with respective thicknesses of 1.7 and 0.7mm. This defines a proton energy cut-off of ~43MeV for coincidence detections. The D1/D2 and D3 main detector entrances have opening angles of 20 degrees and are covered with 2mm and 0.7mm of aluminium, respectively, setting an overall detector cut-off energy of ~20 MeV (D1/D2) and ~0 MeV (D3) for protons. Location on Rosetta ------------------- Diagrams showing the location of the SREM instrument on Rosetta are provided in the ROSETTA_SREM_LOCATION.PDF file available in the DOCUMENTS directory. SREM is located on the +Z panel of the spacecraft (as is most of the science payload). Spacecraft coordinates are provided wrt the launch adapter. SREM is located at: Xsc=+508.95 Ysc=+614.95 Zsc=+2655.00 At an angle of -45degrees from the Ysc axis. Location coordinates on the spacecraft are with respect to the SREM connector, located at: XSREM=-230 YSREM=-106 ZSREM=0 Location of SREM head D12 in spacecraft coordinates, using geometry in Figure 3 of the ROSETTA_SREM_LOCATION.PDF document is: Xsc = 349.1 Ysc = 742.2 Zsc = 2720.8 Location of SREM head D3 in spacecraft coordinates, using geometry in Figure 3 of the ROSETTA_SREM_LOCATION.PDF document is: Xsc = 306.7 Ysc = 699.8 Zsc = 2730.9 Detection Technique ------------------- If a particle is detected by the SREM silicon detectors, a current is generated and the read-out electronics counts the particle. Depending on the amount of energy deposited and which silicon diode(s) it is deposited in, the detected particle is counted in one of 15 channels, which differ in their sensitivity to different particle energies and therefore allow for a certain level of energy resolution and particle species discrimination. The following table provides a list of the 15 SREM channels and the corresponding energy ranges of detected protons and electrons. |======|==========|==========|==========|============| | SREM | Proton Energy [Mev] | Electron Energy [MeV] | |------|----------|----------|----------|------------| | Bin | Emin | Emax | Emin | Emax | |======|==========|==========|==========|============| | TC1 | 27 | infinity | 2.00 | infinity | |------|----------|----------|----------|------------| | S12 | 26 | infinity | 2.08 | infinity | |------|----------|----------|----------|------------| | S13 | 27 | infinity | 2.23 | infinity | |------|----------|----------|----------|------------| | S14 | 24 | 542 | 3.20 | infinity | |------|----------|----------|----------|------------| | S15 | 23 | 434 | 8.18 | infinity | |======|==========|==========|==========|============| | TC2 | 49 | infinity | 2.80 | infinity | |------|----------|----------|----------|------------| | S25 | 48 | 270 | - | - | |------|----------|----------|----------|------------| | C1 | 43 | 86 | - | - | |------|----------|----------|----------|------------| | C2 | 52 | 278 | - | - | |------|----------|----------|----------|------------| | C3 | 76 | 450 | - | - | |------|----------|----------|----------|------------| | C4 | 164 | infinity | 8.10 | infinity | |======|==========|==========|==========|============| | TC3 | 12 | infinity | 0.80 | infinity | |------|----------|----------|----------|------------| | S32 | 12 | infinity | 0.75 | infinity | |------|----------|----------|----------|------------| | S33 | 12 | infinity | 1.05 | infinity | |------|----------|----------|----------|------------| | S34 | 12 | infinity | 2.08 | infinity | |======|==========|==========|==========|============| Table Extracted from [SANDBERGETAL2012] Calibration =========== An essential input for the interpretation of the detection rates, in terms of particle fluxes, are the energy dependent response functions. Therefore, prior to launch, the instruments are fully calibrated at the Proton Irradiation Facility, (PIF) of Paul Scherrer Institut (PSI) [HAJDASETAL1996]. In addition, the instrument and the host spacecraft are simulated with the Geometry and Tracking (GEANT) 3.21 and GEANT4 particle transport codes to accurately determine the response functions to electrons at energies between 0.3 and 15 MeV and to protons in the 8-800 MeV range. Design modularity ================= The Standard Radiation Environment Monitor houses the following functional blocks: - Power supply with DC/DC converter with output voltages for the digital and the analog circuits, as well as for the detectors. - Three particle detectors with associated temperature sensors integrated in the detector housing. - Analog front end with low noise signal amplifiers and signal conditioning electronics. - Comparators with fifteen detection ranges. - Interface for remote total dose and temperature measurement sensors. - Signal processing electronics with host spacecraft interface for: 1. Data processing and storage of scientific data 2. Acquisition of housekeeping data and system health monitoring 3. Telemetry and telecommand interface with host spacecraft. " END_OBJECT = INSTRUMENT_INFORMATION OBJECT = INSTRUMENT_REFERENCE_INFO REFERENCE_KEY_ID = "HAJDASETAL1996" END_OBJECT = INSTRUMENT_REFERENCE_INFO OBJECT = INSTRUMENT_REFERENCE_INFO REFERENCE_KEY_ID = "SANDBERGETAL2012" END_OBJECT = INSTRUMENT_REFERENCE_INFO END_OBJECT = INSTRUMENT END